PARIS — François Fillon will withdraw from the French presidential race next week if a rally of his supporters called for Sunday in Paris fails to be the show of force he expects, one of his closest aides told POLITICO.

“He can fight judges, but he can’t fight his own party for much longer,” said the adviser, who declined to be named.

On Wednesday, the conservative candidate announced that he would soon be placed under formal investigation by judicial authorities over allegations that he had illegally funneled public funds to his wife and children. But, in a defiant speech, he also declared he would stay in the election race — setting in motion a wave of resignations from his campaign team.

The exodus started a few hours after the speech when his top foreign affairs adviser and would-be cabinet minister Bruno Le Maire — himself a losing candidate in the conservative primary last November — called it quits because Fillon had promised he would resign if ever put under formal investigation.

Since then, officials from his Républicains party have deserted the campaign in droves. The supporters of Bordeaux mayor Alain Juppé, who lost to Fillon in the primary’s final round, have all withdrawn. Among the high-profile deserters was Juppé’s former campaign manager Gilles Boyer, who had since become the Fillon campaign treasurer.

The first round of the election takes place on April 23 and the nomination deadline for candidates is just two weeks away.

An aide to Juppé told POLITICO that contrary to media reports suggesting he wasn’t excited at the prospect of running in the election after losing badly in November, the Bordeaux mayor and former prime minister was "warming up" to the idea.

But the party does not have much time to switch to a new candidate. The first round of the election takes place on April 23 and the nomination deadline for candidates is just two weeks away.

Fear of success

Angry Républicains officials cautioned Friday that making Sunday's demonstration a yardstick of Fillon’s support was “meaningless” because catholic right-wingers had organized en masse to send sympathizers to the gathering.

Alain Juppé is said to be "warming up" to the idea of running | Nicolas Tucat/AFP via Getty Images

A former Le Maire supporter, who resigned from the Fillon campaign along with him on Thursday, said that the movement Sens Commun (Common Sense) — which organized within the Républicains four years ago to oppose same-sex marriage, voted into law by the current socialist-led parliament — had mobilized to bring busloads of supporters to Paris.

“It’s quite easy to put a few thousand people on a small esplanade in the posh 16th district and call it success,” the Le Maire aide said.

The fear, in other words, is that Fillon might call the gathering a vibrant demonstration of support, and choose to fight on.

A “draft Juppé” movement started this week to ensure the former prime minister would be able to submit the 500 nominations from national or local elected officials that all presidential candidates must present by March 17. The Constitutional Council, which gathers the endorsements, said Friday it had started to receive some nominations for Juppé.

Even though Juppé seems the most likely candidate to replace Fillon if he withdraws from the race, former president Nicolas Sarkozy, a bitter Juppé rival, has not given up the idea of playing the party’s kingmaker behind the scenes, the Juppé aide noted. Le Monde reported on Friday that two of Fillon’s top supporters — Senate president Gérard Larcher and former Républicains general secretary Bernard Accoyer — met the former French president to discuss "acting very quickly" in the event of a Fillon withdrawal next week.

Leaving the lifeboat

“Fillon is in an impossible situation,” a French conservative MP told POLITICO Friday, explaining: “It has become impossible for us to campaign for him on the ground, we can’t find volunteers to do it, he can’t do radio or TV interviews because he rightly fears the questions will all be about the scandal.”

The MP, who declined to be named because he said he didn’t want to seem to be “joining in the onslaught” against Fillon, added: “If you’re a top campaign guy in Fillon’s team today, you don’t want to be the last one to leave the lifeboat next week, that’s why they’re all leaving."

Bitterness was running high in the Fillon camp Friday, amid a sense that a withdrawal next week was all but certain. One top adviser predicted the election would become a duel between far-right leader Marine Le Pen and centrist Emmanuel Macron. "Fillon’s votes will go partly to these two, and Juppé won’t be able to even reach the 20 percent mark. It’s the end of the [conservative] party,” another top adviser said.

“Plus, now that [Fillon] has been talking like Le Pen for two weeks, we look like a party of extremists” — Alain Juppé aide

The Juppé supporters, on the other hand, accuse Fillon of having led the Républicains to disaster with the stubborn and tone-deaf way he reacted to the allegations that he used public money to pay his wife and children for fake jobs.

“Plus, now that he has been talking like Le Pen for two weeks, we look like a party of extremists,” the Juppé aide said, complaining about the harsh language Fillon has adopted.

Even before the Sunday rally, Fillon will have a chance to test his popularity Saturday when he meets representatives of the so-called “civil society” — personalities from outside politics he enrolled in order to show that he wouldn’t rely just on professional politicians.

But even such a supposedly friendly audience may prove disappointing. According to the Le Maire associate, about half the personalities invited to the meeting have already bowed out.